Electric starter mechanism for internal combustion engines



1965 A. H. SEILLY ETAL 3,210,554

ELECTRIC STARTER MECHANISM FOR INTERNAL COMBUSTION ENGINES Filed AprilI9, 1963 2 Sheets-Sheet 1 Q Q W MQ -N F "i 5 w i 5 nu 22 s x j S Q R Q jw s w 3\ g m a l 2/ b a N N E N a H N I \m OKYL 5, 1965 A s l ETAL3,210,554

ELECTRIC STARTER MECHANISM FOR INTERNAL COMBUSTION ENGINES Filed April19, 1963 2 Sheets-Sheet 2 United States Patent 3,210,554 ELEQTRICSTARTER MECHANISM FOR INTERNAL COMBUSTION ENGINES Alec Harry Seiily,North Wembley, Pierre Henri Peitret, London, and Denis Wheatiey, NewMalden, England, assignors to C.A.V. Limited, London, England Filed Apr.19, 1%3, Ser. No. 274,163 Claims priority, application Great Britain,Apr. 26, 1962, 15,922/62 1 Ciairn. (Cl. 29tl38) This invention relatesto electric starter mechanisms for internal combustion engines, and ofthe kind comprising an electric motor, a shaft extending co-axially fromone end of the rotor, a sleeve surrounding said shaft, a quick pitchscrew-thread or equivalent connection between the sleeve and shaft, apinion formed on, or secured to the sleeve, a solenoid including aspring loaded tubular armature surrounding the sleeve, said solenoidwhen energised being arranged to move the pinion axially on the shaftinto engagement with a toothed wheel of the engine, and a motorcontrolling switch arranged to be closed by the solenoid armature whenthe latter is moved to its fullest extent under energisation.

The object of the invention is to provide such mechanism in a convenientform.

According to the invention a starter mechanism of the kind specifiedcomprises an abutment on the sleeve, an axially movable part on thesolenoid armature disposed to contact the abutment, and resilient meansacting on said part in a direction to urge it towards the pinion, thearrangement being such that in the event of a tooth of the pinionengaging a tooth of the engine wheel endto-end, the solenoid armaturecan be moved against the action of the resilient means into a positionto close the switch.

In the accompanying drawings FIGURES l and 2 respectively are sectionalside and end views of an example of the invention, FIGURE 1 being asection on the line 11 of FIGURE 2, and FIGURE 2 being a section on theline 22 of FIGURE 1.

Referring to the drawings there is provided a substantially cylindricalcasing in which are mounted the stator windings 11 of an electric motor.The rotor 12 of this motor is mounted on a tubular spindle 13surrounding a central shaft 14. One end of the spindle 13 isco-terminous with the adjacent end of the rotor (hereinafter termed thefront end), whilst the rear end of the spindle extends from the rear endof the rotor and has mounted thereon a commutator 15. Also the rear endof the spindle 13 surrounds a bearing bush 16 carried by a centralspigot 17 extending forwardly from the interior of a cap 18 forming arear end closure for the casing 10.

The rear end of the shaft 14 incorporates splines which are formed at avery large helix angle so as to provide an interference engagement withsplines in the spindle 13 so as to prevent both relative axial andangular movements. The shaft 14 extends forwardly to a substantialdistance beyond the forward end of the rotor 12 to provide an extension14a which at its forward end is mounted in a bearing 19 in a cover 20connected to the casing 10. Moreover, within the middle portion of therotor (considered in an axial direction) the shaft 14 is waisted so asto provide a substantial clearance between the spindle 13 and shaft torender the shaft torsionally resilient to a fairly high degree.

A portion of the extension 14a between the front bearing 19 and therotor 12 has formed on it a quick pitch screw-thread having a helixangle of approximately 60. With this portion of the shaft is engaged acomplementary screw-thread formed on the interior of a sleeve 21surrounding the extension 14a. On the front end of the sleeve is formeda pinion 22 which is adapted to be moved axially into engagement with atoothed flywheel 23 of the engine with which the starter mechanism isassociated.

In the cover 24 is mounted the winding 24 of a solenoid. The armature 25of the solenoid, which is loaded towards the rotor 12 of the motor bymeans of a coiled compression spring 26, surrounds the sleeve and is oftubular cylindrical form having a step 25a on its internal periphery. Anannular ring 27 is normally held against the step 25a by means of acoiled compression spring 28 reacting at its other end on an abutmentmounted at the rear end of the armature. Moreover, the inner edge of thering 27 is arranged, when the armature is drawn into the winding againstthe action of the spring 26, to contact an abutment ring 29 located onthe sleeve 21.

The cover 26 is provided at its rear end with a flange which isconnected by screws to a mounting plate 30, the flange and plate beingprovided with registering holes for the reception of bolts whereby themechanism can be mounted on the engine. Since in use, the bolts willserve to clamp the flange and plate together the aforesaid screws may berelatively small. The mounting plate 39 is secured to the casing bymeans of a pair of relatively long bolts 31 extending through the statorcore and rear end cap 18, but between the mounting plate and the casingis interposed a hollow cylindrical part 32 formed from a transparentmaterial such, for example, as a polycarbonate. The ends of the part 32have integral dowels engaging holes in the casing 10 and plate 30respectively so that when the long bolts 31 are in position, the part 32constitutes a rigid forward extension of the casing through which therear end of the sleeve and other associated parts to be referred to canbe viewed.

The pair of long bolts 31 are disposed at 180 to one another relative tothe axis of the shaft, and pivoted about their rearward end portionswithin the cap 13 are a pair of brushes 33 co-operating with thecommutator 15 and connected to the field windings. Another pair ofbrushes 33a disposed at to the pair 33 are mounted about pivots 34extending from an annular carrier 35 through which the bolts 31 extendand clamped in position by the cap 18, the brushes 33a being earthed.

On the mounting plate 30 is the fixed contact 36 of a motor controllingswitch, the moving contact 36a of this switch being carried from therear end of the armature 25 and being arranged to close the switch whenthe armature has been fully drawn forwardly into the winding 24.

Surrounding the rear portion of the sleeve 21 is a collar 37 which isurged forwardly by a coiled compression spring 38 interposed between itand an abutment ring on the sleeve. The internal periphery of the collarat its front end is of truncated conical cam form, and surrounds aplurality of angularly spaced balls 39 located respectively within holesin the sleeve 21. When the sleeve is at its rearward position the balls39 are held by the cam form of the collar in engagement with acircumferential groove 40 in the shaft to locate the pinion againstinadvertent engagement with the flywheel. However, in the forwardposition of the sleeve the balls are urged by the collar into acorresponding number of recesses 41 in the shaft and are held positivelytherein by the rear inner cylindrical surface of the sleeve 37 to locatethe pinion against premature disengagement from the flywheel.

When it is required to start the associated engine, a remote switch isclosed to cause the energisation of the solenoid winding 24. Thearmature 25 is acted upon by the magnetic flux created by the currentflowing in the winding 24, and is moved against the action of the spring26 towards the left as seen in FIGURE 1. After a small movement of thearmature the ring 27 contacts the abutment 29 and the sleeve 21 is alsomoved forwardly by an amount sufiicient to engage the teeth of thepinion 22 with the teeth of the flywheel 23. This movement is permittedbecause the balls 39 are urged outwardly from the groove 40 by therelative movement of the sleeve 21 and shaft 14 and in doing this thecollar 37 is moved against the action of its spring. Moreover, duringthis initial axial movement of the sleeve 21 angular movement isimparted thereto by the screw thread connection between the sleeve andthe shaft 14 and this assists smooth engagement of the teeth of thepinion and the teeth of the flywheel. When the armature 25 has movedfully into its winding the switch contacts 36, 36a are closed to startthe motor and the axial thrust developed on the sleeve as a result ofthe transmission of torque through the quick-pitch thread completes theengagement of the teeth of the pinion with the teeth of the flywheel.When the pinion is fully engaged with the flywheel the balls move intothe recesses 41 and are positively held therein by the collar 37 whichmoves forward under the influence of its spring so that its rear innercylindrical surface contacts the balls.

In the event of a tooth of the pinion 22 engaging a tooth of theflywheel 23 end-to-end and so preventing the engagement as describedtaking place, the armature 25 can still move fully into its winding dueto the permitted relative axial movement of the ring 27 and armatureagainst the action of the spring 28. Thus the motor will be started andwill cause the pinion to be rotated until the aforesaid end-to-endengagement is cleared whereupon partial engagement is effected by thespring 28 and full engagement is effected as described by thequick-pitch screw thread.

When the engine is started, and the remotely disposed switch is opened,the armature 25 will return to its original position under the action ofthe spring 26 and will urge the collar 37 in a direction away from thepinion to allow the balls to be moved out of the recesses 41. At thesame time the switch contacts 36, 36a will be opened and the pinion wilbe moved out of engagement with the flywheel, partly by the action ofthe spring 26 acting on the sleeve via the armature 25, the ring 27 and4 the collar 37, and partly by the action of the quick pitch screwthread. When the sleeve has fully returned to its initial position theballs 39 wil re-engage with the groove 40 in the shaft to preventinadvertent re-engagement of the pinion with the flywheel. If theremotely disposed switch is not released when the engine is started, anoverspeed device such as is described in our co-pending United Statespatent application Serial No. 258,745, filed February 15, 1963, operatesto break the circuit of the solenoid which allows the sequence asdescribed above to take place.

Having thus described our invention what we claim as new and desire tosecure by Letters Patent is:

Starting apparatus comprising an electric motor having a rotor, a shaftextending from one end of said rotor, a sleeve surrounding said shaft, aquick pitch thread connection intermediate the sleeve and shaft, apinion mounted on said sleeve for engagement with a toothed wheel to bedriven, an annular solenoid winding surrounding said sleeve in spacedrelationship thereto, an axially movable annular solenoid armaturesurrounding said sleeve, a step defined on the internal periphery ofsaid armature, an annular part situated adjacent said step, a coiledcompression spring acting intermediate said part and the sleeve forurging said part into contact with said step, an abutment on the sleeveand positioned to be contacted by said part, when the solenoid armatureis moved by the flow of current through the winding, the movement ofsaid armature being imparted to the sleeve so as to cause the pinion tobe engaged with the toothed wheel, said spring being arranged to becompressed to allow the solenoid armature to move to its fullest extentwhen the engagement of the pinion and toothed wheel is hindered, and amotor controlling switch arranged to be closed when the solenoidarmature has moved to its fullest extent.

References Cited by the Examiner UNITED STATES PATENTS 1,883,432 10/32Whitney 123-179 1,905,836 4/33 Fitz Gerald 123179 X 1,970,885 4/34Chilton 123179 X 3,124,694 3/62 Seilly 123-479 FOREIGN PATENTS 902,9968/62 Great Britain.

MARK NEWMAN, Primary Examiner.

RICHARD B. WILKINSON, Examiner.

